/************** * readtest.c * **************/#include <unistd.h>#include <sys/types.h>#include <errno.h>main(){	int pipe_fd[2];	pid_t pid;	char r_buf[100];	char w_buf[4];	char* p_wbuf;	int r_num;	int cmd;		memset(r_buf,0,sizeof(r_buf));	memset(w_buf,0,sizeof(r_buf));	p_wbuf=w_buf;	if(pipe(pipe_fd)<0)	{		printf("pipe create error\n");		return -1;	}		if((pid=fork())==0)	{		printf("\n");		close(pipe_fd[1]);		sleep(3);//確保父進程關閉寫端	    r_num=read(pipe_fd[0],r_buf,100);printf(	"read num is %d   the data read from the pipe is %d\n",r_num,atoi(r_buf));				close(pipe_fd[0]);		exit();	}	else if(pid>0)	{	close(pipe_fd[0]);//read	strcpy(w_buf,"111");	if(write(pipe_fd[1],w_buf,4)!=-1)		printf("parent write over\n");	close(pipe_fd[1]);//write		printf("parent close fd[1] over\n");	sleep(10);	}	}